Ignition system



1969 w. c. J. VAN MASTRIGT 3,422,804

IGNITION SYSTEM Filed May 9, 1966 62 [I /l if I if: 5; WILLIAM C.J. vAgfla ilsggm 0A BY ATTORNEY 1969 w. c. J. VAN- MASTRIGT 3,

IGNITION SYSTEM Filed May 9, 1966 United States Patent 5 Claims ABSTRACT OF THE DISCLOSURE Current through an ignition coil is controlled by a transistor, the conduction and nonconduction of which is determined by a rotatable photo mask interposed between a source of light and a photoelectric device. The transistor conducts when the light path between the light source and photoelectric device is enabled by the mask and is nonconductive when the light path is disabled. Alternatively, the transistor can be conducting when the light path is disabled and nonconducting when the light path is enabled. By causing the ignition spark to occur at the instant the transistor goes from a conducting to a nonconducting condition, which corresponds to the substantially instantaneous transition from disabling to enabling, or enabling to disabling, of the light path between the light source and photoelectric device, the time occurrence of the ignition spark is accurately controlled. Since the time the light path is enabled or disabled does not determine the time occurrence of the ignition spark, the time the light path is enabled and disabled can be controlled to control the time current flows through the primary winding of the ignition coil so as to prevent unnecessary power losses and subsequent heating of the ignition coil.

This invention relates to ignition systems for internal combustion engines and more particularly to an ignition system wherein a semiconductor device, such as a transistor, in series with the primary winding of an ignition coil is caused to be alternately nonconducting and conducting in such a manner that the time of occurrence of an ignition spark is accurately determined for all speeds of the engine.

Conventional internal combustion engines utilize an ignition system which includes an ignition coil, the secondary of which is electrically coupled to spark discharge devices, such as spark plugs, in a predetermined sequence by a high voltage distributor which is synchronized with the speed of the engine. The primary winding of the ignition coil is coupled to a switch known as thebreaker across which is connected a capacitor. Ideally, the operation of this system is such that the primary Winding of the ignition coil has current flow therethrough which is interrupted by the breaker points at the same time that the high voltage distributor is in a position to efiiciently transfer a resulting voltage appearing in the secondary winding of the ignition coil, due to the interruption of current in the primary winding by the breaker, to one of a plurality of spark plugs. Even though highly developed, the breaker points or switch has well known disadvantages that make their use in internal combustion engines undesirable. For example, the breaker points are subject to wear that necessitates their rather frequent replacement. Also, at high engine speeds the breaker points tend to float due to their inertia thereby making sparking undepentdable. Further, the instant a spank takes place with breaker points may vary as a result of such factors as changes in engine speed, spring force, friction, vibration and the like. This is highly undesirable inasmuch as improper time occurrence of ignition sparks increases engine wear and results in inetficient utilization of fuel. Various attempts have been made to overcome the disadvantages of the breaker points by replacing them with other devices.

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Although most of these devices have been successful in eliminating many of the disadvantages of breaker points, they generally have not been successful in precisely controlling the instant an ignition spark occurs throughout the range of engine speeds from very low to very high revolutions per minute. Accordingly, these devices still result in undesirable engine wear and inefficient use of fuel.

Also, the operation of many prior art internal combustion engine ignition systerns is such that current normally flows through the primary winding of the ignition coil and this current flow is only momentarily interrupted to produce an ignition spark. Since current flows through the primary winding most of the time, this results in unnecessary power losses and subsequent heating of the ignition coil. Some systems have attempted to overcome this by utilizing an RC network to prevent current flow in the primary winding for a fixed interval after current is interrupted to cause an ignition spark. This results in the disadvantage that the interval determined by the RC network is fixed for all engine speeds. Therefore, if the period is short enough to allow current in the primary of the ignition coil to build up to a suflicient value before interruption at high engine speeds, the interval during which no current flows in the primary winding at low engine speeds is too short to be of any consequence. Making the time constant of the RC net-work variable with engine speed increases the cost and complexity of the ignition system and decreases reliability of the ignition system due to the added parts and mechanisms. Some ignition systems have been designed so that normally no current flows through the primary winding of the ignition coil until a spark is desired at which time current from a source, such as a charged capacitor, is caused to briefly flow through the primary winding. A severe disadvantage of this type of systern, however, is that the precise time of spark occurrence is not controlled over the range of engine speeds from low to high revolutions per minute.

Further, many prior art ignition systems cause, or enable, current flow through the primary winding of the ignition coil when the ignition key is turned on but the engine is not running. Such continued and uninterrupted current flow may cause the ignition coil to burn out.

Accordingly, one object of this invention is to overcome these and other disadvantages of prior art internal combustion ignition systems.

Another object of this invention is to provide improved ignition apparatus for internal combustion engines.

Still another object of this invention is to provide ignition apparatus for an internal combustion engine in which the time occurrence of ignition sparks are accurately controlled over the entire range of engine speeds to insure efiicient use of fuel, reduced engine wear and increase torque.

Still another object of this invention is to provide ignition apparatus for an internal combustion engine in which an ignition spark occurs when required over the entire range of engine speeds to eliminate missing, or partial firing, which occurred with prior art breaker points.

A further object of this invention is to provide improved ignition apparatus for an internal combustion engine wherein no current fioWs through the ignition coil when the ignition is turned on but the engine is not cranked or running.

The present invention, therefore, relates to an internal combustion engine system which includes a plurality of spark discharge devices, such as spark plugs, for igniting the combustible mixture of said engine by means of an ignition coil having a primary winding and a secondary winding With distributor means for coupling said secondary winding with said spark discharge devices. Briefly described, an improved spark generating apparatus according to this invention comprises a transistor having emitter, collector and base electrodes with the emitter-collector circuit of the transistor being connected between the primary winding of the ignition coil and a source of voltage. A source of radiation and a pick-up device responsive to the radiation is provided with a path for said radiation between said source and said pick-up device. Rotatable means synchronized with the speed of the engine is adapted to alternately enable and disable said radiation path for predetermined time intervals with an abrupt transition between said enabling and disabling and said disabling and said enabling. An amplifier having its input coupled to said pick-up device and its output coupled to the base of said transistor converts the alternate enabling and disabling of said radiation path into corresponding alternate voltage levels or portions having an abrupt transition therebetween such that said transistor is conducting during the occurrence of one voltage portion and nonconducting during the occurrence of the other voltage portion to produce a spark at least at one said spark discharge device for each occurrence of said transition between the voltage portion which causes said transistor to conduct and the voltage portion which causes said transistor to be nonconductive. The rotatable means synchronized with the speed of the engine is adapted to provide an ignition spark generating transition when the distributor is in a position to efficiently transfer a voltage to one of said discharge devices for the entire range of engine speeds.

In accordance with another feature of this invention, means are provided which prevent the transistor from conducting in the absence of rotation of said rotatable means even though the ignition key is turned on.

The exact nature of this invention as well as other objects, features and advantages thereof will be readily apparent from consideration of the following detailed description related to the accompanying drawings in which like reference characters designate like or corresponding parts throughout the several figures and wherein:

FIG. 1 illustrates in schematic form a preferred embodiment of the present invention;

FIGS. 2A, 2B and 2C illustrate various rotatable disks which may be utilized in the apparatus of FIG. 1;

FIG. 3 is a schematic illustration of a transistor amplifier circuit which may be utilized in the apparatus of FIG. 1;

FIG. 4 illustrates various idealized wave shapes in the circuit of FIG. 3 and the apparatus of FIG. 1; and

FIG. 5 illustrates how some of the components of the present invention may be combined within the distributor housing of a conventional internal combustion engine.

Referring now to FIG. 1, the reference character 11 designates an internal combustion engine having eight spark plugs, each of which are designated by the reference numeral 12, for igniting the combustible mixture of the engine. Each spark discharge device or spark plug 12 is coupled to a contact 14 by way of an electrical cable 15. Each contact 14 is located within a high voltage distributor housing 13 which also includes a high voltage distributor rotor 16 which is synchronized with the speed of the engine 11 by means of a suitable coupling, such as a rotatable shaft 34. The high voltage distributor rotor 16 is electrically coupled to the secondary winding 21 of an ignition coil 20 by means of an electrical conductor 17. When driven in synchronism with the engine 11, the distributor rotor 16 will connect, or electrically couple, the secondary winding 21 of the ignition coil 20 with each of the contacts 14 and, therefore, to each of the spark plugs 12 in a predetermined sequence. The operation of the high voltage distributor is such that each time current in the primary winding 22 of the ignition coil 20 is interrupted, a high voltage surge appears in the secondary winding 21 due to the collapse of the magnetic field previously set up by current in the primary winding 22. If, at the same instant the current is interrupted in the primary winding 22, the high voltage distributor 16 is located at one of the contacts 14, the high voltage surge produced in the secondary winding 21 of the ignition coil 20 will be coupled to the associated spark plug 12 to cause an ignition spark. As will now be apparent, a good ignition spark will only be produced if current in the primary winding 22 of the ignition coil 20 is interrupted each time the rotor 16 is in a position to effectively transfer the surge voltage to one of the contacts 14. As will also be apparent, when the engine is running at very high speeds, the distributor rotor 16 is only in position near one of the contacts 14 for a very short period of time which necessitates very accurate timing of current interruption with the rotor 16 to prevent missing (the absence of a desired spark at one or more spark plugs). As will be apparent from the description which follows, the apparatus of the invention accurately synchronizes the interruption of current in the ignition coil with the position of the distributor rotor 16 for the entire range of engine speeds from very low to very high revolutions per minute.

As shown by FIG. 1, the primary winding 22 of the ignition coil 20 is coupled to the collector electrode 26 of a PNP transistor 24, the emitter electrode 25 of which is coupled to source of positive potential, such as the positive side of a battery 18, by way of an ignition switch 23. The other side of the battery 18 is grounded as shown. The base electrode 27 of the transistor 24 is also coupled, by way of a resistor 28, to the same positive potential which is applied to the emitter electrode 25 thereby causing the transistor 24 to be normally nonconductive. Also coupled to the battery 18 by way of the ignition switch 23 is an amplifier 31 and a source of radiation, such as a light bulb 32. The other side of the light bulb 32 is grounded as shown. The amplifier 31 has its output coupled to the base electrode 27 of the transistor 24 and its input coupled to a radiation responsive pick-up device, such as a photodiode 33. A path 36 for the radiation (light) emitted by the source 32 exists between the source 32 and the pick-up device 33. Interposed between the source 32 and the pick-up device 33 so as to be able to block the radiation path 36 is a rotatable fiat disk 35 which is impervious to the radiation given off by the device 32. The disk 35 is positioned so that it is capable of blocking the radiation path 36 at a point between its center and its circumference. The disk 35 is also rotated in synchronism with the engine 11 by being coupled to the shaft 34 which drives the high voltage distributor rotor 16.

The pattern of a disk 35 which may be used with an eight cylinder engine is illustrated by FIG. 2A which shows that the disk includes eight, equally spaced, radially extending areas 37. The portions of the disk 35 which intercept the radiation path 36 when the disk is rotated is indicated by the broken line 38. As shown by FIG. 2A, when the disk is rotated, the radiation path will be blocked or disabled by one of the radially extending areas 37 for a time after which the radiation path will be enabled for a time by the open area between adjacent radially extending areas 37. For each rotation of the disk 35, the light path will be so enabled and disabled eight times which is equal to the number of contacts 14 and spark plugs 12. Also as shown by FIG. 2A, the area of the pick-up device 33 responsive to the radiation is relatively small so that the transition between enabling and disabling and disabling and enabling of the radiation path caused by rotating the disk 35 is very abrupt, being substantially simultaneous.

Referring now to FIGS. 1 and 2A, assume that the ignition switch 23 is closed which supplies operating potential to the transistor 24, the amplifier 31 and the light bulb 32. Since the emitter 25 and base 27 electrodes are at the same potential, the transistor 24 will be nonconductive in the absence of a potential from the output of the amplifier 31 which causes the transitor 24 to conduct current. As will be described below in conjunction with FIG. 3, when the ignition key, or switch, 23 is on, or

closed, the amplifier 31 does not produce an output which enables the transistor 24 to conduct in the absence of rotation of the rotatable disk 35. This eliminates the danger of burning out the ignition coil 20 when the ignition switch 23' is inadvertently left on and the engine 11 is not running.

When the engine 11 is running, the distributor rotor 16 and the disk 35 is rotated in synchronism therewith. This causes the disk 35 to alternaately enable and disable the radiation path 36 with an abrupt transition between the enabling and disabling and disabling and enabling. The photodiode 33 is responsive to the radiation of the light source 32 in such a manner that its resistance is very small during the time period the path 36 is enabled or unblocked by a space between the radially extending areas 37 of the rotating disk 35 and has a very high resistance when the radiation path 36 is disabled or blocked by one of the areas 37 of the rotating disk 35. The photodiode 33 is chosen to have a very fast response time so that the transition between its high and low resistance conditions is very abrupt, being substantially simultaneous. As is described below in conjunction with FIG. 3, the resistance changes of the photodiode, which correspond to the alternate enabling and disabling of the radiation path 36 by the disk 35, are converted into corresponding voltage levels or portions having an abrupt transition therebetween which are amplified by the amplifier 31. Accordingly, the output of the amplifier 31, which is coupled to the base electrode 27 of the transistor 24, comprises two voltage levels or portions having an abrupt transition therebetween with one voltage portion corresponding to and having a time duration equal to the time the radiation path 36 is enabled and the other portion corresponding to and having a time duration equal to the time the radiation path is disabled.

As will be more fully described below, the transistor 24 will remain nonconducting during the occurrence of one voltage portion or level and will be conducting during the occurrence of the other voltage portion or level. As will also be apparent from the description lhereinbelow, the voltage portion which causes the transistor 24 to conduct may correspond to the time the radiation path 36 is disabled or enabled. Conversely, the voltage portion during which the transistor 24 remains nonconductive may correspond to the time the radiation path is enabled or disabled.

Since the primary winding 22 of the ignition coil 20 is coupled to the collector-emitter circuit of the transistor 24, when the transistor 24 conducts a current, the same current will flow through the primary winding 22 of the ignition coil 20. The disk 35 is designed so that the voltage level which causes conduction of the transistor 24 has a sufiicient time duration to permit current through the primary winding 22 to build up to a sufiicient value to cause a high voltage surge in the secondary winding 21, when the current in the primary winding is interrupted, for the highest speed of the engine 11. Also, sufficient time is provided to enable the current to fall to a zero value before the next current build-up time interval, Then the transition between the voltage portion which causes conduction of the transistor 24 and the voltage portion which causes the transistor 24 to be nonconductive occurs, the current in the transistor 24 emitter-collector circuit and the primary winding 22 of the ignition coil is abruptly interrupted. The resulting collapse of the magnetic field previously established by current flow causes a high voltage surge to be developed in the secondary winding 21 of the ignition coil 20 which, as described above, is coupled to one of the spark plugs 12 by the distributor rotor 16 to produce an ignition spark.

As will be apparent, the apparatus of FIGS. 1 and 2A produces an ignition spark each time a transition occurs between enabling and disabling, or disabling and enabling, of the radiation path 3 6 by the rotatable disk 35. As will be apparent from consideration of FIG. 2A, this ignition spark producing transition corresponds to one of the edges of each radially extending area 37 on the rotable disk 35. Each ignition spark producing edge can be located, or formed when the disk 35 is fabricated, to coincide with the distributor rotor 16 being adjacent one of the contacts 14 in the distributor housing 13 such that the voltage surge in the secondary winding 21 is always produced, for the entire range of speeds of the engine 11, at an instant when the distributor rotor 16- is in the most favorable position for transferring a potential to one of the contacts 14. In other words, regardless of the speed of the engine 11, the apparatus of FIGS. 1 and 2A always interrupts the current in the primary winding 22 when the distributor rotor 16 is in the best position to transfer a potential to one of the contacts 14. Such accurate timing of the ignition spark for all engine speeds has not previously been obtained. Further, with the present invention, once the timing is obtained, no further adjustments are required.

The Zener diode 10 connected across the transistor 24 protects, in a well known manner, the transistor 24 from any reverse voltages or currents which may occur when current in the primary winding 22 is interrupted. In order to overcome premature burn-out of the bulb 32, the bulb 32 is preferably aged. Such aged bulbs last about 10,000 hours and should be sufficient for about five to eight years of average driving time.

FIG. 3 illustrates how the photodiode 33 may be incorporated as part of the input circuit of the amplifier 31 and also illustrates, within the slotted outline 49, a multistage transistor amplifier circuit which may be utilized as the amplifier 3 1 of FIG. 1. Reference to FIG. 3 shows that the amplifier comprises three transistor stages including an NPN transistor T1 and two PNP transistors T2 and T3. The base electrode 42 of the transistor T1 is coupled to ground by a resistor 41 and to one side of the ignition switch 23 by way of the photodiode 33 with the photodiode and the resistor 41 constituting a voltage divider network. The other side of the ignition switch 23 is coupled to the positive side of the battery 18 as described above. The emitter 43 of the transistor T1 is coupled to ground and the collector electrode 44 is coupled, by way of the resistor 45, to the ignition switch 23. The transistor T2 has its base electrode 46 coupled to the collector electrode 44 of transistor T1, its collector electrode 47 couple to ground by way of the resistor 48 and its emitter electrode 49 coupled to the ignition switch 23 by way of the resistor 50. The transistor T3 has its base electrode 54 coupled to the emitter electrode of transistor T2 by way of the capacitor 51, its emitter electrode 55 coupled to ground and its collector electrode 56 coupled to the ignition switch 213 by way of the resistor 28. The base electrode 27 of the transistor 24, as described above, is coupled to the output of the multistage amplifier which appears at the collector 56 of the transistor T3 Assume now that the ignition switch 23 is closed and that the engine 11 is not being cranked or running, thereby causing the disk 35 to be stationary. If the disk 35 is in a position to block the radiation path 36, the photodiode 33 will present a very high, or substantially infinite, impedance which causes the base 42 and emitter 43 of the transistor T1 to be at ground potential which causes the transistor 21 to be nonconductive. When the transistor T1 is not conducting, the base 46 and emitter 49 of the transistor T2 are at the same positive potential which causes the transistor T2 to be nonconductive. The base 54 and the emitter 55 of the transistor T3 are at ground potential which renders the transistor T3 nonconductive. When the transistor T3 is nonconductive, the base 27 and the emitter 25 of the transistor 24 are at the same positive potential which renders the transistor 24 nonconductive and, accordingly, no current flows through the primary winding 22 of the ignition coil 20.

Assume now that when the ignition key or switch 23 was closed, the disk 35 was in a position to enable the radiation path 36 which causes the photodiode 33 to have a very small resistance which is less than the resistance of the resistor 41. This causes the base 42 of the transistor T1 to be more positive than the emitter 43 which renders the transistor T1 conductive thereby causing substantially ground potential to be seen at its collector 44. This substantially ground potential is seen at the base 46 of the transistor T2 which causes the transistor T2 to be conductive since the emitter 49 is coupled to a positive potential. Since the disk 35 is not rotating, the conduction of transistors T1 and T2 is a steady state condition which will not be transmitted by the coupling capacitor 51 to the base 54 of the transistor T3. Accordingly, the transistors T3 and 24 will remain nonconducting and no current will flow in the primary winding 22 of the ignition coil 20. As will now be clear, no current flows through the ignition coil in the absence of rotation of the disk even though the ignition switch 23 is closed. This prevents the possibility of burning up the ignition coil 20 when the ignition is inadvertently left on and the engine is not running.

FIG. 4 illustrates various idealized voltage and current wave shapes at different points in the circuit of FIG. 3. Referring now to FIG. 4, a portion of the outer circumferential end portion of the disk 35 has been straightened for purposes of clarity of illustration with the portions of the disk 35 which intercept the radiation path between the light source and the photodiode indicated by the broken line 38. Referring now to FIGS. 3 and 4, during the time periods t1 to 12, t3 to t4 and t5 to 26, when the disk 35 is rotated, a radially extending portion 37 of the disk 35 blocks the radiation path and transistors T1, T2, T3 and 24 are nonconducting in a manner as described above. Accordingly, during these time intervals, the potential appearing on the collector 44 of the transistor T1 and the base of transistor T2 is the positive potential of the battery 18, as illustrated by the wave shape 60; the potential appearing on the base 54 of the transistor T3 is positive, as indicated by the wave shape 61; the potential appearing on the base 27 of the transistor 24 is positive, as indicated by the wave shape 62; and no current flows through the primary winding 22 of the ignition coil, as indicated by the wave shape 63. During the time periods 12 to t3 and 14 to t5, however, the radiation path is enabled by the space between the areas 37 during which time periods the photodiode 33 has a very small resistance which enables conduction of the transistor T1 in a manner as described above. The conduction of transistor T1 during these time intervals causes the potential appearing on its collector 44 to be at substantially ground potential as is illustrated by the wave shape 60. This ground potential appears at the base 46 of the transistor T2 and causes the transistor T2 to also be conducting during these time intervals. As will now be apparent, the enabling and disabling of the radiation path by the rotating disk 35 causes the transistors T1 and T2 to be conducting and nonconducting, respectively, for equal periods of time, thereby producing two corresponding voltage levels or portions having an abrupt transition therebetween as indicated by the wave shape 60. AS shown by FIG. 4, this wave shape resembles a series of square waves which are readily passed through the coupling capacitor 51 to the base 54 of the transistor T3. However, the capacitor 51 will average out the wave shape passing therethrough in a Well known manner so that part of the wave shape is positive and the other is negative as illustrated by the wave shape 61. During the time intervals 22 to t3 and t4 to t5, the potential on the base 54 of the transistor T3 is negative, as shown by the wave shape 61, which causes the transistor T3 to be conductive during these intervals. When transistor T3 is conducting, its collector 56 becomes substantially ground potential, as is shown by the wave shape 62, which is also seen at the base 27 of the transistor 24 to cause transistor 24 to be conducting, thereby causing current to flow in the primary winding 22 of the ignition coil 20 during these time intervals, as shown by the current wave shape 63. Also as shown by the wave shape 63, the current in the primary winding 22 will increase exponentially due to the inductance of the winding.

As shown by FIG. 4, the current in the primary winding 22 is interrupted at times 11, t4, 16, etc., to cause an ignition spark as described above in conjunction with FIGS. 1 and 2A. That is, the circuit of FIG. 3 causes current flow in the primary winding of the ignition coil 20 during each time interval that the radiation path 36 is enabled. This current flow is interrupted to produce an ignition spark during the transition between enabling and disabling of the radiation path and no current is produced in the primary winding of the ignition coil 20 during the time the radiation path is disabled. The time of current flow and the absence of current flow in the primary winding of the ignition coil and the time of an ignition spark can be reversed by changing the PNP transistor T3 to an NPN transistor. For example, if transistor T3 were an NPN type, it would remain nonconductive during the time intervals t2 to t3 and t4 to 15 since the voltage on its base at these time intervals is negative as indicated by the wave shape 61. These time intervals correspond to times when the radiation path 36 is enabled and nonconduction of transistor T3 will prevent conduction of the transistor 24 and no current will flow in the primary windings 22, as described above. During the time intervals [1 to 12, 23 to t4, and t5 to 16 during which the radiation path is disabled, however, the potential on the base of an NPN transistor T3 would be positive which would cause the NPN transistor T3 to be conducting which would cause the transistor 24 to conduct and current would flow in the primary winding of the ignition coil. For an NPN transistor T3, the ignition spark would occur during the transition between disabling and enabling of the radiation path 36.

For purposes of disclosure only, it being understood that the present invention is not limited thereto, the value of the components in the circuit of FIG. 3 may be as follows:

Bulb 32 Chicago Miniature Lamp #CM382.

Photodiode 33 IN2l75.

Resistor 45 27K ohms, /2 watt.

Resistor 50 1K ohms, /2 watt.

Resistor 28 6.8K ohms, /2 watt.

Resistor 58 /2 to 1 ohm, 50 watt.

Resistor 41 1.5K ohms, /2 watt (magnitude determined by type of photodiode used).

Resistor 48 56 ohms, /2 watt.

Resistor 53 560 ohms, /2 watt.

Capacitor 51 mi.

Transistor T1 2N871 (Fairchild).

Transistor T2 2N1183B (RCA).

Transistor T3 2Nl485 (RCA).

Transistor 24 2N1653 (Bendix).

Ignition coil 20 Turns ratio 1:400 or 1:250.

Battery 18 12 volts DC.

The resistor 58 in the collector 25 circuit of the transistor 24 may be used, if desired, to limit current. Also, the transistor 24 and the resistor 58 are preferably coupled to a heat sink (not shown). The circuit of FIG. 3 may also be utilized with a positive grounded battery 18, as will be apparent to those skilled in the art. For a positive grounded. battery 18, however, it is preferred toconnect the primary winding 22 of the ignition coil between the emitter 25 of the transistor 24 and the resistor 58 and to connect the collector 26 of the transistor 24 directly to ground. The number of amplifier stages in the amplifier 4) of FIG. 3 is determined by the number of stages required to produce the current needed to drive the transistor 24. That is, the amplifier 4 9 also functions as a current amplifier. The transistor 24 utilized in one embodiment of the invention was capable of switching 25 amperes at a rate of several megacycles per second which greatly exceeds the spark rate required at the highest engine revolutions per minute. Further, one photodiode 32 which was utilized responded to interrupted light up to a range exceeding 25,000 cycles per second which is also far in excess of the spark rate needed for the highest speed internal combustion engines. Accordingly, the apparatus of this invention is capable of producing an accurately timed spark rate for the highest speed internal combustion engines available. Other sources of radiation may also be used. in place of the light bulb 32. For example, other types of radiation, such as ultraviolet rays, etc., it only being necessary that the disk 35 the impervious to the radiation used and the pick-up device 33 responsive to the radiation.

The above description relates to an eight cylinder engine which utilizes the disk 35 shown in FIG. 2A. However, the apparatus of the present invention may be utilized with internal combustion engines having more or less than eight cylinders. For example, FIG. 2B illustrates a disk which may be utilized with a six cylinder engine and FIG. 2C illustrates a disk which may be utilized with a four cylinder engine. As shown by FIGS. 2A, 2B, and 2C, the number of radially extending areas which disable the radiation path is equal to the number of cylinders (there normally being one spark plug to each cylinder). Also, the number of spaces separating the radially extending areas is equal to the number of cylinders. As described above, an open area may determine the time current flows, or the time current does not flow, in the primary winding of an ignition coil. Conversely, the radially extending areas may determine the time current does not flow, or the time current does flow, in the primary winding of an ignition coil. The ignition spark, however, is always produced at the transition between an open area and a radially extending area or at the transition between a radially extending area and an open area. It

is clear then, that by determining the width of each radially extending area that intercepts the radiation path 36 and the width of each space separating the radially extending areas, the ratio of the time the primary winding of the ignition coil conducts current to the time the primary winding does not conduct current is fixed for all engine speeds without the necessity of using an RC circuit, the time constant of which is varied by the engine speed. In embodiments of the present invention which have been constructed, the time ratio of current flow to no current flow and the time ratio of no current flow to current flow have varied over the range of 25% to 50%. In a high speed, eight cylinder engine, a current flow to no current flow ratio of 1:1 was found to be very satisfactory.

Other rotating disks have been used in the prior art to time the ignition spark of an internal combustion engine. These disks generally contain holes or slots thereon that correspond to the time the ignition spark is to take place. The operation of these devices is such that the entire width of the hole or slot corresponds to the time during which the ignition spark may take place which makes the time occurrence of the ignition spark imprecise. In fact, one prior are device narrowed the width of the holes or slots in an attempt to more closely control the time occurrence of the ignition spark. The width of these openings can be reduced only so much, however, for -if the opening is too narrow, insufficient light impinges upon the pick-up device at high engine speeds and missing, or total failure of the ignition system may take place. Further, very narrow openings do not permit easy control of the ratio of current flow to no current flow in the primary winding of the ignition coil and narrow openings are subject to becoming clogged with dust and oil which makes them impervious to light radiation. The subject invention, however, utilizes the transition between an open space and the disk material itself to precisely and dependably time the occurrence of the ignition spark for all engine speeds with the ratio of open space, or openings, to solid areas of the disk material controlling the ratio of current flow to no current, or no current to current flow, in the ignition coil.

Referring now to FIG. 3, the value of the capacitor 51 is chosen such that it and its associated charging and discharging circuit has a high time constant with respect to the voltage charges which must be passed therethrough for the lowest speeds of the engine 11 (FIG. 1). This is to prevent capacitor 51 from unduly differentiating the voltage wave shape 61 shown in FIG. 4 to an extent that would prevent an ignition spark at the required time. In cold weather and for some engines having a very slow cranking speed, it may be desirable to insure that the wave form 61 is not excessively distorted by the capacitor '51 when the engine is being cranked by a starter or motor (not shown) in order to get the engine started. This can be accomplished by shorting out the capacitor 51 by closing the switch 52. By causing the switch 52 to be closed only during the time the engine is being cranked by the starter motor, none of the advantages of having the capacitor in the circuit are lost. As will be apparent to those skilled in the art, many means can be utilized to insure that the switch 51 is only closed during the time that the engine is being cranked. For example, it would be a simple matter to have the starter switch short out the capacitor 51 during the time the starter switch is activated.

Various components of the apparatus comprising the subject may be conveniently mounted within the distributor housing of an internal combustion engine. Referring now to FIG. 5, a typical distributor housing 70 is illustrated as including a base member 71 which is preferably formed from an electrically insulating material, such as plastic. A distributor cap 72, also formed from an electrically insulating material, is removably secured to the base member 71 by suitable means, such as springs, clips, or the like (not shown). A rotatable shaft 73, corresponding to the shaft 34 of FIG. 1, is driven in synchronism with the engine and extends into the distributor housing 70. Mounted on the shaft 73 is a high voltage distributor base member 79 to which is attached a distributor rotor 75, which corresponds to the rotor 16 of FIG. 1. The rotor is electrically coupled to a spring section 76 which engages a stationary, electrically conductive member 77 which is mounted in the distributor cap 72. The member 77 enables the rotor 75 to be electrically coupled to the secondary winding of an ignition coil by means of an electrical cable (not shown). A plurality of electrical contacts 74, equal to the number of spark plugs used with the associated engine, are also mounted on the cap 72 which includes openings 78 thereon to enable each contact 74 to be connected to its associated spark plug by means of an electrical cable (not shown). These contacts 74 correspond to the contacts 14 of FIG. 1. When the shaft 73 rotates the rotor base member 79, and, therefore, the rotor 75, the rotor will be electrically coupled to the secondary winding of an ignition, at least in part, by the spring 76 and the stationary member 77. Also, in a manner as described above, rotation of the shaft 73 causes the rotor 75 to contact, or come closely adjacent to, each of the contacts 74 to enable a voltage surge to be coupled to the spark plugs in a predetermined sequence. Also mounted to the shaft 73 to be rotatable therewith, is a disk 80 which corresponds to one of the disks illustrated in FIGS. 2A, 2B or 2C and discussed above in conjunction with FIGS. 1, 3 and 4. A source of light 82, corresponding to the radiation source 32 of FIGS. 1 and 3, and a pick-up device 81, corresponding to the device 33 of FIGS. 1 and 3, is mounted on a station.- ary support member 83 such that the disk 80 is enabled to block the radiation path between the source 82 and the device 81 in a manner as described in detail above. Since the disk 80 and the rotor base member 79 are preferably formed from an electrically insulating material, these components may be formed as unitary structure which is mountable on the shaft 73. The pick-up device 81 can readily be coupled to an amplifier, such as illustrated in FIG. 1, by the reference character 31, which is located outside of the distributor housing 70, as are the ignition coil and transistor 24. It is to be understood that FIG. is a simplified illustration of the interior of a distributor housing and does not show other mechanisms normally found therein, such as apparatus which varies the time of ignition spark with respect to the position of pistons within their respective cylinders for various engine speeds, since such apparatus does not comprise a part of the subject invention.

Many modifications and variations of the subject invention are possible in light of the above detailed description. It is, therefore, to be understood that, within the scope of the appended claims, the subject invention may be practiced otherwise than specifically described.

What is claimed is:

1. In an internal combustion engine system having a source of voltage and at least one spark discharge device for igniting the combustible mixture of said engine by means of an ignition coil having a primary winding and a secondary winding with means for coupling said secondary winding to said spark discharge devices, improved spark generating means comprising; a semiconductor device having emitter, oollector, and base electrodes, means coupling the emitter-collector circuit of said transistor to said voltage source and the primary winding of said ignition coil, a source of radiation, a pick-up device responsive to said radiation, a path for said radiation between said source and said pick-up device, rotatable means synchronized with the speed of said engine for alternately enabling and disabling said radiation path for predetermined time intervals with an abrupt transition between said enabling and disabling and said disabling and enabling, amplifier means coupled to said voltage source and having input and output means, said amplifier means having its input coupled to said pick-up device and being adapted to convert said alternate enabling and disabling of said radiation path into corresponding alternate output voltage portions having an abrupt transition therebetween with one voltage portion corresponding to the time the radiation path is disabled and the other voltage portion corresponding to the time the radiation path is enabled, said transistor having its base electrode coupled to said output means of said amplifier means such that said transistor is conducting during the occurrence of one said voltage portion and nonconducting during the occurrence of the other voltage portion thereby causing a spark at least at one said spark discharge device for each occurrence of said abrupt transition between the voltage portion which causes conduction of said transistor and the voltage portion which causes nonconduction of said transistor, and means electrically coupled to said transistor for preventing conduction of said transistor in the absence of rotation of said rotatable means including said amplifier means having at least one stage of amplification and a coupling capacitor electrically coupled between the output of at least one stage of amplification comprising said amplifier means and the base of said transistor.

2. The apparatus according to claim 1 further including means for electrically eliminating said coupling capacitor when said engine is being started.

3. In an internal combustion engine system having a source of voltage and a plurality of spark discharge devices for igniting the combustible mixture of said engine by means of an ignition coil having a primary winding and a secondary winding with distributor means synchronized With the speed of said engine for sequentially coupling said secondary winding to said spark discharge devices, improved spark generating apparatus comprising; a transistor having emitter, collector and base electrodes, means coupling the emitter-collector circuit of said transistor between said voltage source and the primary winding of said ignition coil, a source of radiation, a pick-up device responsive to said radiation, a path for said radiation between said source and said pick-up device, rotatable means synchronized with said distributor means for alternately enabling and disabling said radiation path for predetermined time intervals a number of times for each rotation thereof equal to the number of said spark discharge devices with an abrupt transition between said enabling and disabling and said disabling and enabling, amplifier means coupled to said voltage source and having input and output means, said amplifier having its input coupled to said pick-up device and adapted to convert said alternate enabling and disabling of said radiation path into corresponding alternate output voltage portions having an abrupt transition therebetween with one voltage portion corresponding to the time duration the radiation path is disabled and the other voltage portion corresponding to the time the radiation path is enabled, said rotatable means adapted to enable and disable said radiation path in such a manner that one corresponding voltage portion has a time duration in the range of 25% to of the other said voltage level time duration, said transistor having its base electrode coupled to said output of said amplifier means such that said transistor is conducting during the occurrence of one said voltage portion and nonconducting during the occurrence of the other voltage portion thereby causing a spark at least at one said spark discharge device for each occurrence of said abrupt transition between the voltage portion which causes conduction of said transistor and the voltage portion which causes nonconduction of said transistor, said rotatable means adapted to produce a spark producing transition when said distributor means is in a position to efficiently transfer a voltage in the secondary of said ignition coil to at least one of said spark discharge devices, and means electrically coupled to said transistor to prevent conduction of said transistor in the absence of rotation of said rotatable means.

4. The apparatus according to claim 3 wherein said distributor means, said rotatable means, said source of radiation and said pick-up device are located in a housing.

5. The apparatus according to claim 4 wherein said distributor and said rotatable means constitute a unitary structure.

References Cited UNITED STATES PATENTS 2,084,267 6/1937 Hicks 123--148 3,144,012 8/1964 Tarter. 3,235,742 2/1966 Peters. 3,237,620 3/1966 Hetzler et al. 3,297,009 1/1967 Sasaki et al. 3,324,351 6/1967 Pahl.

LAURENCE M. GOODRIDGE, Primary Examiner.

US. Cl. X.R. 

